Sunan Abī Dāwūd 601

The full narration

Anas b. Malik said; The Messenger of Allah (ﷺ) rode a horse and was thrown off it and his right was grazed. He then prayed one of the prayers sitting and we prayed one of the prayers sitting, and when he finished he said:the Imam is appointed only to be followed ; so when he prays standing, pray standing, and when he bows, bow; when he raises himself, raise yourselves; when he says “Allah listen to him who praises Him”, “Our Lord ! to Thee be the praise”: and when he prays sitting all of you pray sitting